The present invention relates to an optical head for recording or reading data by applying light to an optical disk.
In recent years, as a recording medium for recording an image, an audio or information, an optical disk such as a CD (Compact Disc), a DVD (Digital Versatile Disc) or the like has been employed that can read (or record) the image, the audio or the information by applying light thereto. An optical head is used for applying a laser beam to a recording layer of the optical disk to record data on the recording layer and (or) detecting the laser beam reflected from the recording layer to read the data.
In FIG. 1, an arrangement diagram of the optical head is shown. As shown in FIG. 1, the optical head includes a laser light source Ld, a mirror Mr, a collimator lens Lc, an objective lens Lb, a beam splitter Bs and a light receiving element Pd. A laser beam applied from the laser light source Ld is reflected by the mirror Mr and is incident on the collimator lens Lc. The laser beam incident on the collimator lens Lc is outputted as a parallel light and is incident on the objective lens Lb. The laser beam incident on the objective lens Lb is applied to the recording layer of an optical disk Ds.
At this time, the laser beam is applied so that an image of a laser spot is formed on the recording layer of the optical disk Ds and an optical axis is vertical to the recording layer of the optical disk Ds. The beam splitter Bs is a prism that transmits a part or all of the laser beam outputted from the laser light source Ld and reflects a part or all of the laser beam reflected on the optical disk Ds. The beam splitter Bs serves to guide the laser beam outputted from the laser light source Ld to the recording layer of the optical disk Ds and guide the laser beam reflected by the optical disk Ds to the light receiving element Pd. The light receiving element Pd is an optical element for converting light to an electric current to read data in accordance with the intensity of light.
Since the optical head applies the laser beam to the rotating optical disk, the objective lens for applying the laser beam to the optical disk needs to follow the deviation or the tilt of the optical disk. Thus, the optical head uses a lens holder for holding the objective lens supported by a plurality of metal elastic members (wire springs). The lens holder is driven in a vertical direction (a focusing direction), a rightward and leftward direction (a tracking direction) and a tilting direction (tilt).
FIG. 7 shows a side view of one example of a related optical head. FIG. 8 shows a bottom view of the optical head shown in FIG. 7. The optical head B shown in FIGS. 7 and 8 includes a base 91 to which a collimator lens Lc is attached and an actuator base 92 (designated by an act base 92, hereinafter) in which a lens holder 95 for holding an objective lens Lb. The act base 92 is fixed to the base 91. In the act base 92, a through hole 920 is formed and a laser beam outputted from the collimator lens Lc passes through the through hole 920 and is incident on the objective lens Lb.
In the lens holder 95, coils 954, 955 and 956 are formed for focusing the objective lens Lb to vertically move the objective lens Lb relative to the optical disk, tracking the objective lens Lb to move the objective lens in the radial direction of the optical disk and tilting the objective lens Lb to allow the objective lens to follow the tilt of the optical disk. On the act base 92, a pair of permanent magnets 924 are arranged. The lens holder 95 is disposed in a magnetic field generated by the permanent magnets 924. Thus, a prescribed magnetic field by the permanent magnets 924 acts on the coils 954, 955 and 956. Under this state, when a prescribed current is supplied to the coils 954, 955, and 956, a Lorentz force is exerted on the coils, respectively. The lens holder 95 is driven by this Lorentz force to carry out the focusing, the tracking and the tilting operations of the objective lens Lb, respectively.
The lens holder 95 is supported by a support member 921 provided on the act base 92 through metallic wire springs 922 having an elasticity. The wire springs 922 support the lens holder 95 and are also used as transmission lines for supplying an electric current to the coils 954, 955 and 956. The three wire springs 922 are respectively arranged on both the surface sides of the lens holder 95 and are respectively paired and connected to the coils 954, 955 and 956. The wire springs 922 are soldered to the side surfaces of the lens holder 95 to elastically support the lens holder 95.
On the side surfaces of the support member 921, gel type damping members 925 having a visco-elasticity are arranged to cover the wire springs 922. Thus, the wire springs 922 are restrained from being damped by the damping members 925. On the support member 921, a flexible substrate 923 for supplying an electric current to the wire springs 922 is attached to a surface opposite to the lens holder 95.
The flexible substrate 923 has turning portions 9231 arranged on the side surfaces of the support member 921. On the side surfaces of the support member 921, adhesive recessed groove portions 926 are formed for applying an adhesive agent so that the turning portions 9231 of the flexible substrate 923 are not separated from the support member 921. A thermosetting adhesive agent is injected to the adhesive recessed groove portions 926 to stick the turning portions 9231 of the flexible substrate 923 to the support member 921, so that the turning portions 9231 of the flexible substrate 923 can be prevented from being separated from the support member 921. Further, the adhesive agent can come into contact with the support member 921, the flexible substrate 923 and the act base 92 and firmly adhere these members together so that the members are not respectively separated from others.
On the flexible substrate 923, electric power wiring 927 are formed for supplying an electric power to the wire springs 922. On the turning portions 9231, land portions 9271 are formed in which the electric power wiring 927 are exposed outside. The wire springs 922 are soldered to the land portions 9271 so that the electric power wiring 927 can be electrically conducted to the wire springs 922. Accordingly, the electric power can be supplied respectively to the coils 954, 955 and 956 through the wire springs 922.
JP-A-2005-85310 and JP-A-2002-133684 disclose the other arts related to the present invention
In a producing process of the optical head B, a quantity of injection of the adhesive agent to be injected to the adhesive recessed groove portions 926 is hardly finely controlled. Further, even when the quantity of the injection of the adhesive agent can be controlled, much labor and time are necessary for controlling the quantity of the adhesive agent. As a result, the production cost of the optical head B is increased.
When the quantity of the injection of the adhesive agent cannot be controlled so that the quantity of the adhesive agent is too low, the turning portions 9231 of the flexible substrate 923 cannot be adequately fixed to the support member 921. The land portions 9271 insufficiently come into contact with the wire springs 922. Thus, the electric power may not be sometimes supplied to the coils 954, 955 and 956. Consequently, irradiation accuracy of the laser beam to the optical disk Ds is degraded.
When an excessive adhesive agent is injected to assuredly adhere the turning portions 9231 to the support member 921, the excessive adhesive agent overflowing from the adhesive recessed groove portions 926 sticks to the land portions 9271. When the adhesive agent sticks to the land portions 9271, since the adhesive agent is an insulating material, the adhesive agent prevents the land portions 9271 from being electrically conducted to the coils 954, 955 and 956. Thus, control accuracy of the objective lens Lb is deteriorated. When the control accuracy of the objective lens Lb is deteriorated, accuracy for reading data from the optical disk Ds and (or) recording data on the optical disk Ds by the laser spot is lowered, so that the reliability of the optical head B is deteriorated.
Further, when the excessive adhesive agent adheres to the support member 921 and the act base 92, since the adhesive agent is contracted when the adhesive agent is hardened, an unnecessary stress or strain is generated in the act base 92 or the support member 921. Thus, even under a state that the electric current does not flow, the position of the objective lens Lb may possibly deviate from a prescribed position. Accordingly, there is a fear that the follow-ability of the laser beam relative to the optical disk is deteriorated.
Further, when the thermosetting adhesive agent is injected to the adhesive recessed groove portions 926, in portions surrounded by the adhesive recessed groove portions 926 and the turning portions 9231 of the flexible substrate 923, air in the surrounded portions is hardly vented, so that it takes much time to inject the thermosetting agent and produce the optical head.